There are two categories of truck-mounted carpet cleaning systems. The first category of truck-mounted carpet cleaning systems is direct drive systems, or van-powered systems. These direct drive systems are powered by the engine of the vehicle on which they are installed. The second category of truck-mounted cleaning systems is a slide-in system. Slide-in systems are self-contained units that are powered by their own engines.
Truck-mounted carpet cleaning systems typically employ powerful vacuums, combined with hot water and chemicals to achieve their cleaning results. The hot water serves two purposes during carpet cleaning. First, the hot water helps activate certain types of cleaning chemicals such that they are more effective in cleaning a carpeted surface. Second, the hot water facilitates quicker drying time than does colder water. The hot water is typically generated by passing water through one or more heat exchange devices. Heat can be extracted from the vehicle's engine coolant, the system's engine exhaust, or the blower exhaust.
Typical systems employ multiple heat exchange devices to heat various fluids. For example, one heat exchange device utilizes exhaust from a blower of a vehicle. The temperature of exhaust generated by the blower is generally in the range between about 250 degrees and about 300 degrees Fahrenheit. Employing blower exhaust helps preheat the water to an intermediate temperature, which is less than ideal for cleaning.
The main exchanger utilizes exhaust from the system's engine or the vehicle's engine. This exhaust is much hotter than exhaust collected from the blower, typically in excess of 1000 degrees Fahrenheit. The main exchanger heats the water to the ideal temperature for cleaning, which is between about 230-250 degrees Fahrenheit. However, since the engine exhaust is so hot, it is possible to overheat the water in the exchanger. In order to prevent the water from overheating, some systems are equipped with a heat diverter, which routes all of the high temperature exhaust gases away from the heat exchange device. The systems may be equipped with a bypass system to move heated water out of the system to either a recovery tank or to a fresh water supply tank if the water reaches a predetermined temperature where cooler water can then be drawn into the system.
These described technologies require either diverting an entire source of exhaust (i.e., all of the high temperature exhaust gases) or diverting and controlling a number of fluid flows to maintain a suitable water temperature. The downside of these solutions is that they require a complete diversion system that is separate from the heat exchange device along with a number of complicated valves and sensors. Also, some heat exchange devices do not have multiple exhaust sources (i.e., a source of somewhat hot exhaust and a source of very hot exhaust). For these types of systems it is very difficult to accurately control the temperature of the water or other fluids by diverting the sole supply of exhaust.